27" iMac GPU heat (late 2012)

That doesn't sound unreasonable to me. I hit 85C on the GPU playing NFS: Most Wanted in Windows 7 on my 2012 iMac (680GTX), and 87C with an overclock.

 

sounds perfectly normal. temps can shoot up or down in a matter of seconds.

 

Everything around 100 °C is perfectly normal for Ivy Bridge processors (Desktop/Mobile). And do me a favor, do not check the GPU/CPU temps! Thank you very much! This is really useless, especially with Turbo Boost 2.0 or newer.

 

Heat dissipation is one of those things the iMac design does not do very well. The form factor just doesn't allow heat to escape very well. While it is true that Ivy Bridge processors run hot, the combo of the iMac form factor and such a hot chip, means a pretty little space heater.

 

Try rev up the fans and see if things get better.

 

Actually, it makes perfect sense. But if you want to return your iMac and not listen to anyone here, you're more than welcome to.

Again, this is an all-in-one system. The temperature of some of the components can get warm, so hitting 91C in 2 minutes is NOT unusual at all. I hit 87C in Need for Speed Most Wanted in under 60 seconds of gameplay in Boot Camp on my iMac, so I'm not sure how you've decided that "75-80 tops after a long session is sensible." The iMac wasn't designed around what Dykstra thinks is sensible.

So again, return the iMac if it doesn't behave like you want it to. But the reality of it + gaming is what you're experiencing. I'm not even entirely sure what's bothering you...

 

My Late 2012 iMac has a i7 Quad with Turboboost! (works on every Turboboost'ed Intel CPU)

The CPU is fast enough. Why not disable Turboboost to safe energy and reduce heat.

When in Windows:

In control panel -> Power Options -> Edit power plan -> Change advanced power settings -> Processor power management -> Maximum processor state. I set it to <100%. (use 99 %)

Also affects the GPU "a bit"

cheers

 

I have never hit 91C, even with fairly aggressive GPU overclocking, and I game for several hours at a time. So, it should not be necessary to have those high temperatures , just turn off turbo boost, and set a static higher fanspeed while gaming (1800-2500rpm depending on the game).

 

Its possible that the fans just hadnt spun up when you checked the temperature. 5 minutes later it might have been different. I dont know.
Also some games, even undemanding ones use the GPU to 100% so the heat produced is the same to a game that is demanding and also used the GPU to the max.

 

Also don't forget your temps are greatly influenced by the ambient temperature. If your rooms hot, the PC/iMac will run hot.

 

It may also be that video intense apps induces more heat since the GPU has to work harder.